1. Field of the Invention
The present invention relates to an automatic analyzer which performs qualitative and quantitative analyses of a biological sample, such as blood, urine, etc. More particularly, the invention relates to an automatic analyzer which is provided with a quality control function.
2. Description of the Related Art
An automatic analyzer performing qualitative and quantitative analyses of a biological sample, such as blood, urine, and the like, mixes a reagent which reacts with a component under measurement in the sample, and measures reagent color variations and the luminescence of a labeled substance contained in the reagent in order to perform analysis. In this case, measurement values may vary due to aging of the reagent, aging of the optical system including a photometer, a photoelectron multiplier, or the like, and variations in the dispensing quality of dispensing and stirring mechanisms, and the like. Therefore, today's automatic analyzers periodically create a calibration curve by using a known amount of standard sample (calibrator) and check the validity of a measured concentration by using a quality control sample (control substance), thus controlling the measurement quality. These quality control procedures are periodically performed in order to ensure that measurement results of the sample are correct. In routine tests, quality control for clinical testing equipment such as a biochemistry automatic analyzer, or the like is indispensable for stably acquiring exact data without being affected by reagent properties, machine troubles, and the like. Approaches for quality control include internal quality control and external quality control. With internal quality control, measurement value variations are observed for each individual apparatus on a daily basis (individual variation) and in units of several days to several months (day-to-day variation). With external quality control, in order to obtain the same measurement results in every hospital, measurements are performed by using the same standard samples in different inspection institutions for correcting measurement variations among the different inspection institutions.
One quality control method is to evaluate the accuracy of measurements by using standard substances. Specifically, this method performs the steps of:
repetitively performing measurement with a target measuring instrument by using standard substances (quality control samples such as standard liquids or control substances) having a known or constant concentration; and determining the average, the variation range, and the like of measurement values to supervise whether or not the measurement process is stable.
The above-mentioned controlled data is generally represented as a control chart which is a statistical method for setting a quality control limit range statistically obtained and checking whether the measurement process is stable or maintained in a stable state.
When a measurement value controlled in this way exceeds the quality control limit range, it is necessary to investigate the cause and restore the measurement process to the stable state. The above-mentioned measurement value deviation is possibly caused by various factors such as the standard liquids, control substances, or reagents used for measurement, as well as the experimental environment (temperature, humidity, and the like) and facilities or measuring instruments (abnormal temperature of constant-temperature bath, a degraded lamp, or the like in the case of biochemistry analyzers).
Conventional automatic analyzers, on the contrary, perform quality control through the steps of: plotting a control chart; recording information such as the replacement date of reagent, a lamp, or the like in a recording section; and displaying the information in the control chart together with quality control values. In this case, the user visually determines the cause of control value deviation based on the user's experiences. Recent years have seen an international trend of numerical value calibration and certainty check based not on the former quality control techniques but on the uncertainty (parameters accompanying measurement results for characterizing value variation which can rationally be associated with measured quantities). The definition and calculation method of the uncertainty used for quality control have come to be widely known by the establishment of ISO15189 (Medical laboratories—Particular requirements for quality and competence) and the promotion activities of the Japanese Standards Association, and the like. The above-mentioned former techniques are disclosed in JP-A-6-281656, Japanese Patent No. 3420791, JP-A-2000-266756, JP-A-2000-187037, and Non-patent References 1 and 2.    Non-patent Reference 1: Academic Journal of Japanese Association of Clinical Laboratory Automation (JSCLA), Vol. 32, No. 1, pp. 19-25: A Study for Measurement Uncertainty in Routine Test using Automatic Analyzer    Non-patent Reference 2: Clinical Chemistry, Vol. 36, Supplementary No. 1, pp. 151-153, 2007: Uncertainty of Routine Test Values Transmitted from Standard System